Sheet-like superabsorbent structures

ABSTRACT

The invention relates to sheet-like absorbents for water and aqueous solutions, containing at a defined distribution 
     A) at least one water-swellable synthetic and/or natural superabsorbent polymer, and 
     B) at least one water-soluble synthetic and/or natural polymer 
     as a matrix of sheet-like design wherein the superabsorbent component A) is integrated or fixed. The sheet-like absorbents have an increased absorptive capacity for water and aqueous liquids, particularly under load. They are manufactured by forming a sheet-like matrix from the water-soluble synthetic and/or natural polymers B) and providing same with said water-swellable synthetic and/or natural superabsorber A), e.g., by applying a solution of matrix B) on a surface, sprinkling same with component A), and drying the sheet-like structure thus obtained. Such sheet-like absorbents are used in hygienic articles, as components in natural or artificial soils, as insulating material for pipes and lines, primarily cables and building constructions, as liquid-absorbing and liquid-storing component in packaging materials, as a part in articles of clothing, and as a depot for the controlled release of an active substance.

The invention relates to sheet-like absorbents for water and aqueoussolutions, a process for the production of said sheet-like absorbents,and their use.

Sheet-like absorbents present the possibility of fixing superabsorbentpolymers (SAP) in the form of a powder or granulate in any desiredarrangement in/on one or multiple sheets. Said fixation is then carriedout in the optimum form for later use, such as in diapers for babies,adult incontinence articles, cable sheathings, soil conditioners,packaging inserts in the food industry, for animal hygiene, wounddressings, and cloths.

For later use, in order to achieve optimum distribution of a powderedsuperabsorbent polymer and to fix same, various methods have beendescribed.

EP 212,618 B1 describes diaper constructions wherein polymerizateshaving a specific grain size distribution are distributed in a cellulosefiber layer. However, such a construction is insufficiently stable withrespect to the distribution of the superabsorbent polymer; inparticular, the distribution of the SAP may be altered undesirablyduring transportation, resulting in non-uniform absorption, e.g., in adiaper.

Another method of fixing powdered superabsorbent polymers in a specificarrangement is described in EP 425,269 A2, according to which the SAPsare bound to thermoplastic, water-insoluble fibers. Binding the SAP tothe fiber is effected in such a way that a slightly surface-melted fiberis contacted with the powdered superabsorbent polymer. The fibersthemselves are fixed among one another in the same manner. Thedisadvantage of this process is that the absorptive capacity of thepowdered superabsorbent polymer is not utilized in full extent. Part ofthe SAP is covered by the thermoplastic and thus not reached by water oraqueous solutions.

EP 547,474 A1 describes a process for the production of absorbingmaterials wherein superabsorbent polymers are distributed. Theabsorptive capacity of the absorbing materials thus obtained is lowerthan the ratio of SAP incorporated in these materials would suggest,i.e., part of the SAP is blocked as a result of the selection ofmaterials used and the production process employed. Moreover, the typeof matrix material used is limited in that the melting point of thismaterial must be above the decomposition temperature of the SAP.

EP 303,445 A1 describes an absorbent sheet material wherein awater-containing SAP has been fixed on a support. The use of thisstructure is limited to a patch used as drug reservoir.

JP Application No. 75-85462 describes a method of producingsuperabsorbent sheets made of a starch/graft polymer integrated in awater-soluble, film-forming polymer.

As an indispensable third component, this document mentions a materialserving as base material. The superabsorbent polymer is fixed on saidbase material together with the soluble, film-forming polymer.

EP 604,730 A1 describes SAP-containing structures which decompose inwater. In addition to the SAP, dispersible polymers and plasticizers arementioned as indispensable components. The structures manufacturedaccording to this application do by no means meet the demand for adefined arrangement of a superabsorber in a matrix, because the methodsdescribed in this document, such as extrusion, mixing or blending, areabsolutely unsuitable for this purpose.

After disintegration of the described sheet materials, particles remainin addition to the superabsorber; consequently, the matrix material isnot soluble in water.

It is therefore the object of the present invention to provide asuperabsorbent sheet having a defined arrangement of superabsorbentpolymers at full utilization of the swelling capacity of thesuperabsorbent polymers, i.e., without loss of absorptive capacity.

It is another object of the invention to find production processesaccording to which such a sheet can be manufactured in an uncomplicatedand cost-effective way. In addition, the sheet should not be fixed to asubstrate, as described in the Japanese patent application No. 75-85462,so that such a sheet can be used more universally.

Said object is achieved by a sheet-like absorbent structure for water oraqueous liquids, containing

A) at least one water-swellable synthetic and/or natural polymer and

B) at least one water-soluble synthetic and/or natural polymer,

wherein component A is integrated or fixed in a defined fashion inmatrix component B having sheet-like design.

This combination does not reduce the absorptive capacity of thesuperabsorbent polymer, since the matrix dissolves on contact with wateror aqueous liquids and therefore, does not impede swelling of the SAP.This embodiment permits controlling the absorption rate for water oraqueous liquids of the absorbent of the invention; in addition, theflexibility of such an absorbent body may be adjusted according to theintended use.

As a basis for the matrix, both synthetic, water-soluble, film-formingpolymers such as polyvinyl alcohols, polyalkyl allyl ethers, polyglycolethers, polyvinylpyrrolidones, polyacrylates, polymethacrylates, as wellas derivatives and copolymers thereof, and natural, water-soluble,film-forming polymers, such as guar, alginates, agar-agar, xanthan,pectin, and starch and the like, as well as chemically modified rawmaterials, such as ethers and/or esters and/or hydrolyzates and/oroxidation products of polysaccharides or proteins, such as cellulose,amylose, starch, or wheat gluten are possible, as are copolymerizatesand/or graft polymerizates based on natural or synthetic polymers.

Not least, the selection of the matrix material depends on the intendedend use. Due to the matrix material, the flexibility of thesuperabsorbent sheet may be varied within a wide range. In a givenmatrix, the flexibility of the superabsorbent sheet may also be variedby using additives such as plasticizers or plasticizing agents like2-ethylhexanol, glycerol and phthalic esters, but also by using fillers,such as chalk, pigments and fibers.

The basis of the SAP employed may he both a synthetic material, such asa water-swellable polymer and/or copolymer based on (meth)acrylic acid,(meth)acrylonitrile, (meth)acrylamide, vinyl acetate, vinylpyrrolidone,vinylpyridine, maleic acid (anhydride), itaconic acid (anhydride),fumaric acid, vinylsulfonic acid, and the salts, amides, N-alkylderivatives, N,N-dialkyl derivatives and esters of these polymerizableacids, and a material of native origin, such as products of guar seedmeal, carboxymethylcellulose, xanthan, alginates, gum arabic,hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, starchand starch derivatives, as well as partially crosslinked productsthereof. Likewise, mixtures or copolymerizates and/or graftpolymerizates of the above-mentioned components may be used.

Preferred materials are partially neutralized, slightly crosslinkedpolymers and copolymers of acrylic acid and acrylamide, graftpolymerizates of starch, as well as crosslinked starches and cellulosederivatives. Suitable products include, e.g., the commercially availableFAVOR and Stockosorb® types of Chemische Fabrik Stockhausen GmbH,Germany.

The grain size distribution of the powdered superabsorbent polymeremployed may vary within wide limits--grains ranging from 0.1 μm to upto 20,000 μm are possible. Preferred grain fractions are in the range offrom 1 μm to up to 5,000 μm. Particularly preferred are grain fractionsranging from 20 to 1,000 μm.

The grain fraction of SAP, which is incorporated in the sheet, cruciallydepends on the intended end use of the film. While grain fractions ofabout 500 μm are normally used in diapers, grain fractions of about1,000 μm are preferred in agriculture, and those around 100 μm andsmaller are preferred in the cable industry.

According to the invention, the superabsorbent sheet is produced bycombining the above-mentioned components. To this end, a viscoussolution of the water-soluble polymer is applied on a sheet, such as asheet metal, siliconized paper, or a PTFE film using suitableprocedures, such as spraying, spreading and knife-coating.

The sheet may be a flat large-area structure as well as the surface of asphere.

Subsequently, the water-soluble polymer on the sheet is sprinkled with asuperabsorbent polymer. The product thus obtained is dried at suitabletemperatures, i.e., at temperatures between those usually employed infreeze drying and 300° C., preferably at temperatures between 50° C. and240° C., optionally under reduced pressure.

Microwave or freeze drying techniques may also be used to dry the sheetmaterial.

During the production of the absorbent sheet materials, particularly indrying thereof, chemical or physical binding between the matrix materialB and the absorbing component A may possibly occur. As an example ofchemical binding, the esterification reaction should be mentioned here,which may occur between carboxyl and hydroxyl groups. Physical bondsresult, e.g., from loop formation or entanglement of the polymermolecules at the surface region of component A or by interactions offunctional groups of the polymer molecules in the components A and B.

After drying, the superabsorbent sheet material is removed from theauxiliary surface used.

According to the invention, another preferred production of thesuperabsorbent sheet is performed by sprinkling a film or some othersheet formed from the matrix material with an SAP, and subsequentlymoistening the mixture with water or an aqueous solution or some othersolvent mixture, or by sprinkling a film or some other sheet formed fromthe matrix material with a moistened SAP and subsequently drying saidsheet.

According to the invention, another preferred production of thesuperabsorbent sheet is performed by sprinkling a film or some othersheet formed from the matrix material with an SAP, and heating thismixture until the matrix material is softened. The sheet thus formed maythen additionally be calendered to improve fixation of thesuperabsorbent polymer in the matrix. This process involves theprecondition that the matrix material used be thermoplastic.

Another preferred production of an absorbent sheet material according tothe invention is carried out by extruding the matrix material. The SAPin a suitable form (with respect to grain size and metering procedure)is added to the matrix material prior to, during, or after extrusion.

Then, a defined arrangement of the SAP in a sheet may also be obtainedby extruding the matrix material together with the SAP into fibers, andsubsequently arranging these fibers in a sheet-like manner by means ofsuitable methods (air stream, blow molding).

Such a defined arrangement may easily be realized during the productionprocess by using a template, or by using specific sprinklingarrangements during application of the powdered superabsorbent polymer.Layering multiple superabsorbent sheets allows spatially definedabsorber structures to be generated which, in addition, may have anabsorption gradient.

Optionally, a sheet material according to the invention may also beformed directly during the production of a water-soluble film, whichmeans that the superabsorber is directly incorporated in the sheet-likematrix during a suitable processing step in the production of same.

The ratio of superabsorbent polymer and matrix may be varied within widelimits; it may range between matrix:SAP=1:1,000 to 100:1. Ratios ofmatrix:SAP=1:100 to 10:1 are preferred, with ratios of matrix:SAP=1:25to 2:1 being particularly preferred.

While in diaper construction, as a rule, high SAP and low matrixconcentrations are desirable, lower SAP concentrations are frequentlypreferred in other fields for planting pots or inserts in foodstuffpackagings. Thus, the SAP/matrix ratio essentially depends on theintended use.

The thickness of the absorbent sheet may be influenced by both theamount of matrix used and the particle size and amount of the SAP used.It may be between 0.2 μm and 30,000 μm; sheets having a thickness offrom 1 to 6,000 μm are preferred; particularly preferred is a sheetthickness of between 20 μm and 2,000 μm. The thickness of the absorbentsheet must also be adapted to the intended end use. Thus, the layerthickness of a sheet intended for use in diaper constructions orfeminine hygiene articles must be as thin as possible to increase thewearing property of the diaper. In the case of sheets intended for adepot formulation, a greater thickness may result in a desirable delayof depot material release.

Surprisingly, it was found that these sheets have an absorptive capacityfor water or aqueous solutions, which is in accordance with the amountof incorporated superabsorbent material. There is no loss in absorptivecapacity of the superabsorber as might be expected as a result of thepresence of the matrix material. This applies to the overall absorptionand the retention (absorption with subsequent pressure load) as well asthe absorption during pressure load (absorption under load).

Surprisingly, it was also found that she absorption rate for water oraqueous solutions of such sheets depends on the ratio of matrix materialand superabsorbent polymer. Consequently, the absorption rate may becontrolled by the ratio SAP/matrix and, of course, by the type of matrixmaterial as well, namely such that a higher matrix ratio results in areduction of the absorption rate.

The superabsorbent sheets according to the invention meet the demand fora defined arrangement of the superabsorbent polymer on a sheet, whichcan advantageously be used in hygienic articles. The advantages of thedefined arrangement of superabsorbers in hygienic articles have beendescribed in EP 212,618 B1; they result, for example, from the fact thatthe liquid load in a diaper is not uniform. Thus, sites of high and lowSAP concentrations are required in a diaper.

Test Methods:

Tea Bag Test (TBT)

To determine the absorptive capacity, the TBT was carried out. A 0.9%NaCl-solution was used as test solution (unless otherwise stated).

A piece of material containing about 0.2 g of SAP is punched out of theabsorbing sheet. This piece is weighed into a tea bag. Subsequently, thetea bag is placed into the test solution for a defined period of time.After draining for 5 minutes, the tea bag was weighed out (determinationof TBT max.) and subsequently, the tea bag was centrifuged in acentrifuge (commercially available spin dryer, 1,400 rpm). Thereafter,weighing is carried out again (determination of TBT ret.).

Using multiple tests employing the same material and varying immersiontimes, the absorption as a function of immersion time (absorption rate)of the superabsorbent sheet material for water or aqueous solutions canbe determined. The absorption of liquid is calculated relative to either1 g of sheet, 1 g of SAP employed, or 1 m² of sheet.

Absorption Under Load (AUL)

To determine the liquid absorption capacity under pressure, the"absorption under load" was determined as described in EP 339,461.

Departing from said procedure, a circular piece of the superabsorbentbody having the size of the inner diameter of the AUL crucible was usedas test substance. The absorption of liquid is calculated relative toeither 1 g of body, 1 g of SAP employed, or 1 m² of body.

DESCRIPTION OF THE FIGURES

FIG. 1 Sprinkling frame

1--(bright area) penetrable part of the sprinkling frame

2--(dark area) impenetrable part of the sprinkling frame

FIG. 2 Diaper construction

1--Laminates of polypropylene covering fleece and polyethylene film

2--Leakage protection with incorporated rubber threads

3--Covering fleece made of polypropylene

4--Polyethylene film on the back side

5--Core envelope made of cellulose fibers

6--Core containing the superabsorbent sheet material

The invention will be illustrated with reference to the followingexamples.

EXAMPLES 1-3

A highly viscous solution is prepared from 25 g of Vinol® 205(water-soluble polyvinyl alcohol) and 75 g of deionized water. A part ofthis solution (cf., Table) is uniformly spread on a sheet (Teflon-coatedfilm or the like) of 270 cm². The sheet thus formed is sprinkled withabout 30 g of FAVOR® SXM 100 superabsorber (slightly crosslinked,partially neutralized polyacrylate) and then dried for 5 minutes at atemperature of 180° C. Subsequently, the unfixed part of thesuperabsorber is removed using a brush. Flexible, superabsorbent sheetsare obtained which can easily be removed from the surface (Teflon-coatedfilm).

                                      TABLE 1                                     __________________________________________________________________________    The Table shows the dependence of the absorption                              rate on the matrix:SAP ratio, a decreasing matrix ratio                       resulting in faster absorption.                                                                TBT (30 sec.)                                                                        TBT (60 sec.)                                                                        TBT (30 min.)*                                    Solution                                                                          SAP Vinol ®205                                                                      max./ret.                                                                            max./ret.                                                                            max./ret.                                      Ex.                                                                              [g] [g/m.sup.2 ]                                                                      [g/m.sup.2 ]                                                                        [g/g]/[g/g]                                                                          [g/g]/[g/g]                                                                          [g/g]/[g/g]                                    __________________________________________________________________________    1  10  226 93    6/6    9/9    50/31                                          2  5   182 46    7/7    12/12  50/31                                          3  2.5 203 23    9/9    13/13  50/31                                          SXM                                                                              0   --   0    9/9    14/14  50/31                                          100                                                                           __________________________________________________________________________     The TBT values marked with * relate to the amount of superabsorber used,      the other TBT values relate to the weight per unit area.                 

EXAMPLE 4

The same procedure as in Example 2 is used, however, a solution of 1 gof Mowiol® 4/88 (water-soluble polyvinyl alcohol of Hoechst AG) and 3 gof water is charged on a sheet of 476 cm². After processing (cf.,Examples 1-3) a flexible film is obtained having a superabsorber ratioof 189 g/m² ; the ratio of Mowiol® 4/88 is 21 g/m².

TBT: max./ret. [l/m² ]/[l/m² ]=9.4/5.8; AUL (2×10³ Pa)=5.7 l/m².

EXAMPLE 5

The procedure is as in Example 4, however, Mowiol® 5/88 (water-solublepolyvinyl alcohol of Hoechst AG) is used instead of Mowiol® 4/88. Afterprocessing (cf., Examples 1-3) a flexible film is obtained which has asuperabsorber ratio of 144 g/m² ; the ratio of Mowiol® 5/88 is 21 g/m².

TBT: max./ret. [l/m² ]/[l/m² ]=7.2/4.4; AUL (2×10³ Pa)=4.4 l/m².

EXAMPLE 6

A solution of 200 g of deionized water, 50 g of glycerol, and 10 g ofguar seed meal (type 104 of Roeper company) is stirred to make ahomogeneous solution. The solution is spread on a sheet of 3,000 cm² andsprinkled with 100 g of FAVOR® SXM 100. The sheet is dried at 75° C. for4 hours and subsequently, the non-adhering SAP is removed using a softbrush.

An absorbent sheet of moderate flexibility is obtained, having an SAPratio of 200 g/m².

EXAMPLE 7

The procedure is as in Example 6, however, carboxymethylcellulose (typeWalocel® 40000 of the Wolf Walsrode company) is used instead of guarseed meal. In addition, drying is effected at 130° C. for 30 minutes.The sheet thus obtained is flexible and has an SAP ratio of 180 g/m².

EXAMPLE 8

The procedure is as in Example 7, however, Acrakonz® BN (soluble,slightly crosslinked, anionic emulsion polymerizate based on acrylicacid derivatives of Chemische Fabrik Stockhausen GmbH) is used insteadof carboxymethylcellulose. In accordance with the concentration ofAcrakonz® BN, a correspondingly larger amount (24 g) of this product isused. The sheet thus obtained is flexible and has an SAP ratio of 240g/m².

                  TABLE 2                                                         ______________________________________                                        The Table shows the dependence of the absorption                              rate on the type of matrix materials used                                                    TBT (30 sec.)                                                                            TBT (60 sec.)                                                                           TBT (300 sec.)                                  SAP      max./ret.  max./ret. max./ret.                                 Ex.-No.                                                                             [g/m.sup.2 ]                                                                           [g/g]/[g/g]                                                                              [g/g]/[g/g]                                                                             [g/g]/[g/g]                               ______________________________________                                        6     200      6/6        15/15     21/16                                     7     180      7/7        10/10     13/13                                     8     240      5/5        10/8      18/15                                     ______________________________________                                         The TBT values relate to the weight per unit area.                       

EXAMPLE 9

One square meter of a polyvinyl alcohol film (Reel L336; W/O 1483 ofAquafilm Ltd., 20 μm in thickness) is sprayed with 50 ml of a solutionof 50% water and 50% ethyl alcohol and subsequently sprinkled with 400 gof FAVOR® SXM 100. The powder is slightly pressed against the surface.Thereafter, drying is effected for 5 minutes at 120° C.

The non-fixed portion of SXM 100 is removed using a vacuum cleaner; 113g/m² remain.

TBT: max./ret. [l/m² ]/[l/m² ]=5.7/3.5; AUL (2×10³ Pa)=3.5 l/m².

EXAMPLE 10

One square meter of a polyvinyl alcohol film (REEL L336; W/O 1483 ofAquafilm Ltd., 50 μm in thickness) is sprayed with 50 ml of a solutionof 50% water and 50% ethyl alcohol and then sprinkled with 400 g ofFAVOR® SXM 100. The powder is slightly pressed against the surface.Subsequently, drying is effected for 5 minutes at 120 C.

The non-fixed portion of SXM 100 is removed using a vacuum cleaner; 179g/m² remain.

TBT: max./ret. [l/m² ]/[l/m² ]=8.9/5.5; AUL (2×10³ Pa)=5.4 l/m².

EXAMPLE 11

A solution of 2 g of Vinol 205, 2 g of glycerol, and 6 g of water isdistributed over a Teflon-coated film on an area of 14×44 cm. Then, atemplate (cf., FIG. 1) is placed thereon. The free areas are sprinkledwith 9 g of Favor SXM 100. The sheet is dried for 5 minutes at 140° C.in a circulating air oven. Subsequently, it is sprayed with a solutionof 0.25 g of Vinol 205, 0.25 g of glycerol, and 1.5 g of water. Then,drying is effected again under the above-mentioned conditions.

The sheet thus obtained is removed from the Teflon-coated film. It isflexible and has an absorptive capacity corresponding to that of thesuperabsorber used.

EXAMPLE 12

Example 11 is repeated; however, no glycerol is used. The resultingsheet is hard, brittle and scarcely flexible. It has an absorptivecapacity corresponding to that of the superabsorber used.

EXAMPLE 13

A solution of 2 g of Vinol 205, 2 g of glycerol, and 6 g of water isdistributed over a Teflon-coated film on an area of 14×44 cm. Then, atemplate (cf., FIG. 1) is placed thereon. The free areas are sprinkledwith 6 g of Favor SXM 100. The sheet is dried for 5 minutes at 140° C.in a circulating air oven.

Subsequently, it is sprayed with a solution of 0.25 g of Vinol 205, 0.25g of glycerol, and 1.5 g of water. Again, the template is placedthereon. The free areas are sprinkled with 4.5 g of Favor SXM 100.Subsequently, drying is effected again under the above-mentionedconditions.

Spraying, placing the template and SAP sprinkling are repeated oncemore, using 2.5 g of SAP.

Finally, spraying and drying are carried out once more. The sheet thusobtained is removed from the Teflon-coated film. It is flexible and hasan absorptive capacity corresponding to that of the superabsorberarranged in all spatial directions in a defined manner.

EXAMPLE 14

One square meter of a polyvinyl alcohol film (Reel L336; W/O 1483 ofAquafilm Ltd., 20 μm in thickness) is sprinkled with 50 g of FAVOR® SXM100. The powder is slightly pressed against the surface. Subsequently, asecond film of the same material is placed thereon. The sheet is coveredwith a Teflon-coated film and ironed (the iron is set to 180° C.) untilthe PVA films and the superabsorber have melted into one another. Theabsorptive capacity of the sheet corresponds to the amount of SAP used.

EXAMPLE 15

According to FIG. 2, a diaper is constructed using the film produced inExample 13. The PE film used and the polypropylene covering fleece arematerials from a diaper production. The sheet produced in Example 13 isused as core (6).

EXAMPLE 16

10×15 cm of the sheet described in Example 2 is placed in a packagingpan and covered with a commercially available kitchen tissue (Kleenex).A deep-frozen chicken (850 g) is placed on the tissue. The entire thawedwater (test period 18 h) is absorbed by the sheet of the invention.

EXAMPLE 17

Example 12 is repeated without a template. Instead of Favor, Stockosorb400 (slightly crosslinked copolymer based on acrylamide) was used.Strips of 1×7.5 cm in size were cut from this sheet. Eight of the stripswere completely inserted into a cylindrical flowerpot (height: 10 cm,diameter: 8.5 cm) containing soil. The soil is kept moist for 5 days.Thereafter, the film had dissolved, the SAP was in the soil in anarrangement suitable, e.g., for plant cultivation.

EXAMPLE 18

Example 1 is repeated; however, instead of Favor, the same amount of thesuperabsorbent depot agent formulation described in Example 9 ofPCT/EP93/01060 is used.

1 cm² of the sheet thus obtained is welded in a tea bag. The tea bag issuspended in 50 ml of a 0.2% saline solution for one hour. The saltsolution is renewed after one hour.

Even after the 5th cycle, the blue coloration of the saline solutionindicates release of the active substance.

EXAMPLE 19

A sheet produced according to Example 10 is ironed according to themethod described in Example 14 onto a fabric as used to sheathe cables.The composite of the sheet of the invention and the fabric has highmechanical stability, the fabric tape has retained its flexibility, theabsorption corresponds to the SAP ratio.

FIG. 1 shows the template used in Example 11.

FIG. 2 shows the diaper construction of Example 15.

We claim:
 1. A sheet-like absorbent for water or aqueous liquids,comprising:A) at least one water-swellable polymer, and B) at least onewater-soluble polymer,wherein component B forms a sheet-like matrix, andcomponent A is incorporated in or attached to the matrix in a definedarrangement.
 2. A sheet-like absorbent according to claim 1, whereincomponent A comprises at least one polymer or copolymer of at least onepolymerizable monomer selected from the group consisting of acrylicacid, methacrylic acid, acrylonitrile, methacrylonitrile, acrylamide,methacrylamide, vinyl acetate, vinyl alcohol, vinylpyrrolidone,vinylpyridine, maleic acid, maleic anhydride, itaconic acid, itaconicanhydride, fumaric acid, vinylsulfonic acid, and amides, N-alkylderivatives, N,N-dialkyl derivatives and esters thereof.
 3. A sheet-likeabsorbent according to claim 1, wherein component A comprises at leastone slightly cross-linked, natural polymer selected from the groupconsisting of guar seed meal, carboxymethylcellulose, xanthan,alginates, gum arabic, chitin, chltosan, agar-agar,hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, starch,and starch derivatives.
 4. A sheet-like absorbent according to claim 3,wherein component A comprises a mixture of at least two of saidpolymers.
 5. A sheet-like absorbent according to claim 1, whereincomponent B comprises at least one water-soluble polymer or copolymer ofat least one polymerizable monomer selected from the group consisting ofacrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile,acrylamide, methacrylamide, vinyl acetate, vinyl alcohol,vinylpyrrolidone, vinylpyridine, maleic acid, maleic anhydride, itaconicacid, itaconic anhydride, fumaric acid, vinylsulfonic acid, and amides,N-alkyl derivatives, N,N-dialkyl derivatives and esters thereof.
 6. Asheet-like absorbent according to claim 1, wherein component B comprisesat least one soluble natural polymer selected from the group consitingof guar seed meal, carboxymethylcellulose, xanthan, alginates, gumarabic, chitin, chitosan, agar-agar, hydroxyethylcellulose,hydroxypropylcellulose, methylcellulose, starch, and starch derivatives.7. A sheet-like absorbent according to claims 6, wherein component Bcomprises a mixture of at least two of said polymers.
 8. A sheet-likeabsorbent according to claim 1, wherein components B and A are presentin a ratio B:A of from 1:1,000 to 100:1.
 9. A sheet-like absorbentaccording to claim 8, wherein components B and A are present in a weightratio B:A of from 1:100 to 10:1.
 10. A sheet-like absorbent according toclaim 9, wherein components B and A are present in a weight ratio B:A offrom 1:25 to 2:1.
 11. A sheet-like absorbent according to claim 1,wherein components A and B are partially reacted chemically with eachother.
 12. A sheet-like absorbent according to claim 1, wherein thecomponents A and B are only physically linked to each other.
 13. Asheet-like absorbent according to claim 1, wherein said absorbent is inthe form of a film, sheet, foil, rolled article, or a laminate.
 14. Aprocess for producing a sheet-like absorbent, said process comprisingthe steps of:forming a sheet-like matrix comprising at least onewater-soluble polymer B; and incorporating or attaching awater-swellable polymer A to the matrix.
 15. A process according toclaim 14, comprising the steps of:a) preparing an aqueous solution ofcomponent B; b) applying the solution from step a) to a support; c)sprinkling the solution-covered support from step b) with component A toobtain a composite material, and d) drying the composite material fromstep c).
 16. A process according to claim 14, wherein steps b) and c)are repeated.
 17. A process according to claim 16, wherein steps b), c)and d) are repeated.
 18. A process according to claim 15, wherein theabsorbent is subjected to a final treatment consisting of steps b) andd).
 19. A process according to claim 15, wherein in step b) the solutionof component B is applied by spreading, knife-coating, spraying,pouring, lick-rolling or trickling.
 20. A process according to claim 14,comprising the steps of:a) disposing a material of component A on asurface of a film of component B, and b) contacting the film with asolvent for component B so that the film is solubilized but notdissolved, and c) drying the resulting product.
 21. A process accordingto claim 20, wherein the film of component B is first contacted with thesolvent and then component A is sprinkled on the surface of the film.22. A process according to claim 20, wherein steps a) and b) arerepeated several times.
 23. A process according to claim 20, wherein theabsorbent are covered with a final film of component B.
 24. A processaccording to claim 20, wherein the film is contacted with the solvent byapplying the solvent by spreading, knife-coating, spraying, pouring,lick-rolling or trickling.
 25. A process according to claim 15,comprising the steps of:a) mixing a solvent for component B withcomponent A to form a mixture; b) contacting a film of component B withthe mixture from step a) to obtain a composite product, and c) dryingthe composite product from step b).
 26. A process according to claim 25,wherein steps a) and b) are repeated several times.
 27. A processaccording to claim 25, further comprising the step of covering the driedproduct from step c) with a film of component B.
 28. A process accordingto claim 15, comprising the steps of:a) sprinkling a film of component Bwith a polymer of component A, and b) thereafter fixing the polymer ofcomponent A to the film by application of heat, pressure or acombination of heat and pressure.
 29. A process according to claim 28,wherein the product from step b) is covered with another film ofcomponent B and thereafter subjected to a heat treatment.
 30. A processaccording to claim 28, wherein the polymer of component A is fixed tothe film of component B by a heat treatment, further comprising the stepof covering the fixed product from step b) with a film after said heattreatment.
 31. A process according to claim 28, wherein steps a) and b)are repeated several times.
 32. A process for producing a sheet-likeabsorbent comprising a matrix of at least one water soluble polymer Bhaving incorporated therein at least one water-swellable polymer A,wherein the matrix is produced by extrusion and component A isincorporated in component B during the extrusion.
 33. A processaccording to claim 32, wherein component A is sprinkled through atemplate, whereby component A is deposited in a pattern defined by saidtemplate.
 34. A process according to claim 15, wherein component A issprinkled through a template, whereby component A is deposited in apattern defined by said template.
 35. A method of absorbing an aqueousliquid, said method comprising contacting said liquid with an absorbentcomprising a sheet-like matrix of at least one water-soluble polymer Bhaving at least one water swellable polymer A incorporated therein orattached thereto.
 36. A method according to claim 35, wherein saidaqueous liquid is a body fluid.
 37. A method according to claim 35, saidmethod comprising incorporating said absorbent agent in a plant growthor storage medium, and moistening said medium, whereby moisture isretained in said medium.
 38. A method according to claim 35, whereinsaid agent comprises an absorbent web, said method comprising wrappingsaid web around a pipe, wire or fiber optic cable, whereby said pipe,wire or fiber optic cable is insulated and shielded against moisture.39. A method according to claim 35, wherein said agent comprises anabsorbent web, said method comprising applying said web to an externalwall of a building, whereby said wall is insulated and shielded againstmoisture.
 40. A method according to claim 35, wherein said agent is apackaging material, said method comprising packing an article in saidmaterial, whereby the packed article is shielded against moisture.
 41. Amethod according to claim 35, wherein said agent is incorporated in anarticle of clothing, whereby a wearer of said article of clothing isshielded against dampness.
 42. A method according to claim 35, whereinsaid agent is a reservoir for controlled release of an aqueous fluid,said method comprising contacting said agent with said fluid andthereafter placing said agent in an environment to be supplied with saidfluid, whereby said agent gradually releases said fluid into saidenvironment.
 43. A sheet-like absorbent according to claim 12, whereinthe components A and B are physically linked by a physical bond selectedfrom the group consisting of loop formation, entanglement of polymermolecules at a surface region of component A, and interaction offunctional groups of components A and B.